(a) Field of the Invention
This invention relates to methods of making loosening preventing nuts.
(b) Description of the Prior Art
There is already known such method of making loosening preventing nuts as is shown, for example, in FIG. 1 wherein a nut 11 is cut down on one end side to be flat and circular to form a recess 12 and crown-shaped part 13, is cut off in the opposite angle parts of this crown-shaped part to be V-shaped, is then compressed in the axial direction with a die D to bend the opposite angle parts inward, is threaded with the same screw 13a as of the screw part 11a on the inner periphery of the tip of the crown-shaped part and is then again compressed with the same die to reduce the inside diameter of the crown-shaped part. In this nut, there are problems that the step of cutting off the opposite angle parts to be V-shaped is a bottle neck to the continuous operation, toils are required for the production and the cost is high.